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United States Patent |
5,000,141
|
Sugano
|
March 19, 1991
|
Crankshaft assembly
Abstract
A crankshaft assembly used in an internal combustion engine comprises: a
crankshaft adjusted in dynamic balance in a manner such that it produces a
predetermined inertia couple as it rotates; a pulley provided at one end
of the crankshaft; a flywheel provided at the other end of the crankshaft;
and balance adjust parts respectively formed in the pulley and flywheel
for counterbalancing the inertia couple produced by the crankshaft, so
that the crankshaft assembly is balanced statically and dynamically. It is
possible to reduce the length of the engine by employing this crankshaft
assembly without increasing the width and height of the engine.
Inventors:
|
Sugano; Tomohiro (Fujisawa, JP)
|
Assignee:
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Isuzu Motors Limited (Tokyo, JP)
|
Appl. No.:
|
396166 |
Filed:
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July 31, 1989 |
Foreign Application Priority Data
| Aug 04, 1988[JP] | 63-193388 |
Current U.S. Class: |
123/192.2; 29/888.08; 74/603 |
Intern'l Class: |
F02B 075/06 |
Field of Search: |
123/192 B,55 VS
74/603
29/901,888.08,888.1
|
References Cited
U.S. Patent Documents
4538481 | Sep., 1985 | Ohta et al. | 123/192.
|
Foreign Patent Documents |
47-29106 | Jun., 1972 | JP | 74/603.
|
701235 | Dec., 1953 | GB | 74/603.
|
757529 | Sep., 1956 | GB | 74/603.
|
Primary Examiner: Kamen; Noah P.
Attorney, Agent or Firm: Gossett; Dykema
Claims
What is claimed is:
1. A method of manufacturing a crankshaft assembly adapted for use in an
internal combustion engine, the crankshaft assembly having a plurality of
crankpins, comprising the steps of:
(A) adjusting a crankshaft in dynamic balance in a manner such that the
crankshaft produces a nonzero predetermined inertia couple when the engine
rotates, the crankshaft having an axis in its longitudinal direction;
(B) adjusting a pulley in dynamic balance in a manner such that the pulley
produces a first inertia couple for partially counterbalancing the
predetermined inertia couple;
(C) mounting the pulley at one end of the crankshaft;
(D) adjusting a flywheel in dynamic balance in a manner such that the
flywheel produces a second inertia couple for counterbalancing a remainder
of the predetermined inertia couple; and
(E) mounting the flywheel at the other end of the crankshaft.
2. The method of claim 1, wherein said inertia couple is an inertia couple
produced around an axis perpendicular to the axis of the crankshaft.
3. The method of claim 1, wherein step (B) includes mounting a first weight
on the pulley and step (D) includes mounting a second weight on the
flywheel.
4. The method of claim 2, wherein step (B) includes mounting a first weight
on the pulley and step (D) includes mounting a second weight on the
flywheel.
5. The method of claim 1, wherein step (B) includes forming a first balance
adjust part on the pulley at a position spaced apart from the center of
the pulley and step (D) includes forming a second balance adjust part on
the flywheel at a position spaced apart from the center of the flywheel.
6. The method of claim 2, wherein step (B) includes forming a first balance
adjust part on the pulley at a position spaced apart from the center of
the pulley and step (D) includes forming a second balance adjust part on
the flywheel at a position spaced apart from the center of the flywheel.
7. The method of claim 1, wherein step (B) includes forming a first balance
adjust part on the pulley at a predetermined position and step (D)
includes forming a second balance adjust part on the flywheel at a
position spaced 180 degrees about the axis of the crankshaft.
8. The method of claim 2, wherein step (B) includes forming a first balance
adjust part on the pulley at a predetermined position and step (D)
includes forming a second balance adjust part on the flywheel at a
position spaced 180 degrees about the axis of the crankshaft.
9. The method of claim 1, wherein step (B) includes forming a first balance
adjust part on the pulley at a position opposite an adjacent crankpin and
step (D) includes forming a second balance adjust part on the flywheel at
a position opposite an adjacent crankpin.
10. The method of claim 2, wherein step (B) includes forming a first
balance adjust part on the pulley at a position opposite an adjacent
crankpin and step (D) includes forming a second balance adjust part on the
flywheel at a position opposite an adjacent crankpin.
11. The method of claim 1, wherein step (B) includes forming a first
balance adjust part on the pulley as an integral part of the pulley and
step (D) includes forming a second balance adjust part on the flywheel as
an integral part of the flywheel.
12. The method of claim 2, wherein step (B) includes forming a first
balance adjust part on the pulley as an integral part of the pulley and
step (D) includes forming a second balance adjust part on the flywheel as
an integral part of the flywheel.
Description
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a crankshaft assembly of an internal
combustion engine, and particularly to a crankshaft assembly of a compact
V-type engine.
2. Background Art
The crankshaft assembly of an internal combustion engine must possess
dynamic balance as well as static balance in order to restrict undesired
vibration. More specifically, the sums of inertia forces and inertia
couples of the crankshaft assembly have to be adjusted to substantially
zero.
Referring to FIG. 3 of the accompanying drawings, a crankshaft 1 of a
six-cylinder V-type engine comprises crankpins 2, 3, 4, 5, 6 and 7 spaced
apart from each other by predetermined angles in the circumferential
direction of the crankshaft 1, crankjournals 8, 9, 10 and 11 respectively
supported by bearing members (not shown) of a crankcase (not shown), and
crankarms 12, 13, 14, 15, 16, 17, 51, 52 and 53 for connecting the
crankpins with the crankjournals. The crankshaft changes the reciprocation
of a piston (not shown) to rotation. The crankarms 12-17 and 51-53 are
respectively provided with balance weights in a manner such that both
total static balance (inertia forces) and dynamic balance (inertia
couples) of the crankarms become zero. The crankshaft can rotate smoothly
or with less vibration and noise due to the balance weights. The balance
adjustment of the crankshaft assembly during assembly generally depends on
dummy weights mounted on the crankpins 2-7.
The crankshaft is also provided with a pulley 19 at one end 18 thereof
(front end) and a flywheel 21 at the other end 20 thereof (rear end). The
pulley 19 drives, for example, a generator and an air conditioner
compressor mounted in the engine via a belt. The flywheel helps maintain
smooth continuous rotation of the crankshaft and transmits driving power.
In the engine having the crankshaft of FIG. 3, a couple is produced due to
an arrangement of the crankpins 2-7 when the crankshaft 1 rotates.
Specifically, the resultant force of centrifugal forces (inertia)
resulting from reciprocating members, such as pistons, piston rings, and
gyrating masses which are considered attached to the crankpins 2-7 becomes
zero, as viewed in the axial direction of the crankshaft, as long as the
crankpins are equal to each other in weight. In this case, however, a
clockwise moment (inertia couple) appears around the center point 0 of the
crankshaft. Therefore, the inertia couple should be eliminated when the
crankshaft 1 rotates within the speed of ordinary operational range, in
order to prevent noise and vibration.
Conventionally, the crankshaft 1 is provided with balance weights 23 at
positions opposite the dummy weights 22 so as to balance with the dummy
weights, as schematically shown in FIG. 4, in order to eliminate the
inertia couple. In such an adjustment, in most cases, the crankarms 12 and
17, which are the furthest crankarms from the center 0, are made thicker
(thicker portions serve as the balance weights) rather than attaching real
bodies. The crankarms 12 and 17 are chosen since a larger moment is
produced in the case where the balance weights are mounted on the furthest
crankarms than the case where the weights are the balance weights and are
mounted on the crankarms 13 and 16.
Although compact engines are well known in the art, there is a demand for
even smaller engines. In designing an engine generally, the balance
weights required for the crankshaft are determined by the piston,
connecting rods and other fundamental elements of the engine. Therefore,
the engine has to be designed larger in height and width in order to
reduce the length thereof. In this case, the distance from the center axis
40 to the balance weight becomes large. An engine smaller in height and
width (thicker balance weights) can be designed if a longer dimension is
allowed in the longitudinal direction of the engine. In other words,
something has to be sacrificed, and it is difficult to design an engine
more compact than conventional compact engines by adjusting the balance of
the crankshaft itself.
Another well-known way of balancing with the dummy weights 22 is
schematically illustrated in FIG. 5. In this case, the balance of each
element, such as crankshaft 1 and the flywheel 21, is ignored. Importance
is placed on the balance of the combination of the crankshaft 1, pulley
19, the flywheel 21, and the dummy weights 22. Therefore, the pulley 19
and the flywheel 21, which have been separately manufactured as balanced
members, are provided with imbalances (24) equivalent to the balance
weights of the crankshaft such that the combination of the elements is
made balanced. In this arrangement, the length of the crankshaft does not
elongate, and the weight of the same does not increase. However, the
damper pulley 19 and the flywheel 21 are provided with the imbalances
prior to assembly. This means that a particular set of the pulley and
flywheel is only usable with a corresponding particular crankshaft and
engine. Therefore, if there is mismatching, the combined elements cannot
function properly in the product. Also, an exchange of he flywheel and
damper pulley is generally impossible.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a crankshaft assembly of
an engine which is compact, easy to assemble and maintain, and comprises
exchangeable elements only.
The above object is attained by a crankshaft assembly comprising: a
crankshaft having a dynamic imbalance which causes an inertia couple in a
particular direction as it rotates; a pulley provided at one end of the
crankshaft; a flywheel provided at the other end of the crankshaft; and
balance adjusting parts respectively formed in the flywheel and pulley so
as to have an imbalance, which causes a couple in a certain direction,
such that they eliminate the inertia couple produced by the crankshaft.
The inertia couple produced due to the rotation of the crankshaft is
counterbalanced by another inertia produced due to the rotation of the
balance-adjust-part-provided-pulley and flywheel. Therefore, it is not
necessary to make the crankarms thicker. In other words, it is possible to
manufacture the crankshaft assembly more compactly. Also, unlike the prior
art arrangement illustrated in FIG. 5, severe limitations are not imposed
in assembling the elements or in exchanging the flywheel and pulley.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a lateral view of a crankshaft assembly of an internal combustion
engine according to the present invention;
FIG. 2 is a schematic view of FIG. 1 which is useful to explain the dynamic
balance of the crankshaft assembly;
FIG. 3 is a lateral view of a prior art crankshaft assembly of a V6 engine;
FIG. 4 is a schematic view useful to explain the dynamic balance of the
crankshaft assembly of FIG. 3; and
FIG. 5 is a schematic view useful to explain the dynamic balance of another
prior art crankshaft assembly.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A preferred embodiment of the present invention will now be explained with
reference to the accompanying drawings.
Referring to FIG. 1, depicted is a crankshaft assembly of an internal
combustion engine (a V6 engine in this particular embodiment) according to
the present invention.
The crankshaft 31, like the prior art arrangement, comprises crankpins 2-7,
crankjournals 8-11 and crankarms 13-16 and 51-53. However, balance weights
are not provided on the crankarms 32 and 33 near the ends of the
crankshaft; instead, these crankarms are made equal to other crankarms
13-16 and 51-53 in thickness. In other words, unlike the prior art
arrangement illustrated in FIG. 4, the end crankarms 32 and 33 are not
provided with balance weights to balance with the dummy weights during
assembly.
A balance adjust part 35, which is a significant part of the present
invention, is formed within the pulley 34. The balance adjust part 35 is
formed apart from the center axis 40 of the pulley 34 and includes a
weight 38 having a mass of ml for counterbalancing the inertia couple
produced by the crankshaft 31. Compared with the prior art arrangement,
the mass ml corresponds to the balance weight mounted on the crankarm 32.
Also, another balance adjust part 37 which includes a weight 39 having a
mass of m2 is formed in the flywheel 36. This balance adjust part 37
corresponds to another balance weight mounted on the crankarm 33.
The balance adjust parts 35 and 37 are positioned opposite to each other or
are positioned with a 180 degree phase difference around the center axis
40 of the crankshaft 31. Also, the balance adjust part 35 is formed at a
position opposite the adjacent crankpin 2, and the balance adjust part 37
is formed opposite the adjacent crankpin 7. The pulley 34 and flywheel 36
are coaxial to the crankshaft 31.
Referring now to FIG. 2, as the crankshaft 31 rotates upon movement of a
piston (not shown), inertia forces F1, F2 and F3 are respectively produced
at the crankpins and consequently an inertia couple M.sub.F is produced
around the x axis perpendicular to the crankshaft axis 40 as well as to
the drawing. The pulley 34 and flywheel 36 produce forces of inertia f1
and f2 by the imbalances m1 and m2 respectively, thereby producing another
inertia couple M.sub.f equivalent to the inertia couple M.sub.F but
opposite in direction. Therefore, the inertia couple M.sub.F is
counterbalanced, whereby the crankshaft assembly is made balanced as a
whole.
In manufacturing the elements of the crankshaft assembly, some elements
possess certain imbalance. Specifically, the balance adjust part 35 of the
pulley 34 and the balance adjust part 37 of the flywheel 36 are shaped in
a manner such that they can produce the inertia forces f1 and f2
respectively. Before adjusting the balance of the crankshaft assembly, for
instance, by a balance adjusting machine, the crankshaft 31 is provided
with the dummy weights w1, w2 and w3 at the crankpins 2-7. In this manner,
accuracy of each element such as the crankshaft 31, damper pulley 34 and
flywheel 36, is maintained, and therefore a compact crankshaft assembly
can be manufactured.
In actually assembling the crankshaft, pulley and flywheel, respective
amounts of the imbalances formed in the elements will be evaluated as
satisfactory if the error drops within a predetermined range, for example
between 8 and 15 g/cm. Also, when a balance adjusting machine of the type
employing a master work is used to form the balance adjust parts, the
balance adjust parts 35 and 37 may be easily formed during dynamic balance
adjustment of the crankshaft assembly during the calibration by the
balance adjusting machine which employs a master work possessing
imbalances m1 and m2 beforehand.
Therefore, it is possible to reduce the length of the crankshaft 31 since
the dynamic balance of the crankshaft 31 is ensured by the pulley 34 and
flywheel 36. As a result, a much more compact engine can be manufactured.
For instance, when the crankshaft assembly of the present invention is
used in a compact engine having a length of 470 mm, the engine length can
be reduced by some 19 mm since the crankarms 32 and 33 can be made
thinner. Also, since the elements are separately adjusted in balance
beforehand, unlike the prior art arrangement illustrated in FIG. 5, no
severe limitations are imposed on assembly and exchanging the elements.
Although the above embodiment only deals with a V6 engine, the principle of
the present invention can be applied to an engine having an asymmetrical
crankshaft, for example, a two-, four-, eight- or ten-cylinder engine.
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